08 December 2011

How Our Brains Keep Us Focused

Efficient selection of sensory signals representing the target of focal attention can account for improved behavioral performance. A) When subject is trying to focus attention on one target (yellow highlighted stimulus in right panel) and ignore distractors (blue highlighted stimuli), neural responses were increased in occipital visual areas of the brain. B) When subjects distributed attention across four stimuli, signals from distracters (blue arrows) had the same magnitude as signals from the target (yellow arrow), causing both relevant and irrelevant information to be routed to perceptual areas of the brain and resulting in less discriminable neural response (more overlap between blue and yellow distributions).

Scientists at the RIKEN Brain Science Institute (BSI) in Japan, have uncovered mechanisms that help our brain to focus by efficiently routing only relevant information to perceptual brain regions. The study will appear in the science magazine Neuron. The results provide valuable insights on how our brains achieve such focus and on how this focus can be disrupted, suggesting new ways of presenting information that augment the brain's natural focal capabilities.

How can the brain be able to focus attention given the many distractions around?

The study points out that the answer may lie in two distinct processes; the "sensitivity enhancement" and the "efficient selection". Sensitivity enhancement corresponds to improvements in how neurons in the cortex represent sensory information like sounds and lights, similar to the volume control or reception control on a television set. Efficient selection is more like a filter, routing important sensory information to higher-order perceptual areas of the brain while suppressing disruptions from irrelevant information.

Video: Nicholas Carr - Memory can only hold between two and four items at a time.

With their research in Neuron, Justin Gardner and colleagues at the RIKEN BSI set out to put these hypotheses to the test and determine which of them plays a dominant role in perception. To do so, they measured brain activity using functional magnetic resonance imaging (fMRI) while human subjects either focused their attention on a single visual location, or distributed their attention across multiple locations. To evaluate results, they used computational models about how brain signals should change based on how well subjects were able to focus their attention.

What they found was that the computational model that best captured the brain activity in the human subjects was the one in which sensory signals were efficiently selected. The model also made a prediction about what kind of stimuli are particularly disruptive to our ability to focus, suggesting that signals which evoke high neural activity are preferentially passed on to perceptual areas of the brain: stimuli with high contrast that evoke large sensory responses, such as flashing lights or loud noises, can thus disrupt our ability to focus. While shedding light on the origins of perception, the results also hint at new ways of presenting information that capitalize on increasing neural activity to help our brains focus, promising applications in the development of critical information display technologies. The findings also offer insights into the causes of common attention-related disorders such as attention deficit hyperactivity disorder (ADHD).

RIKEN is Japan's flagship research institute devoted to basic and applied research. Over 2500 papers by RIKEN researchers are published every year in reputable scientific and technical journals, covering topics ranging across a broad spectrum of disciplines including physics, chemistry, biology, medical science and engineering. RIKEN's advanced research environment and strong emphasis on interdisciplinary collaboration has earned itself an unparalleled reputation for scientific excellence in Japan and around the world.

The RIKEN Brain Science Institute (BSI) was established as an institute at RIKEN in October, 1997 to answer a growing need in society for cutting-edge brain science research. Since its establishment, BSI has attracted promising scientists domestically and internationally and brought together diverse research and human resources, and today enjoys an international reputation as an innovative center for brain science.